Question : how many back end server can I have with 2003 Exchange

I'm running Exchange 2003 with 1 frontend server and 1 backend server.  I would like to add 1 more backend server.  Is this possible?  Can EACH backend server have a 75 gb database?

Answer : how many back end server can I have with 2003 Exchange

Yes, you can do that.  That is how companies that are spread across WAN sites with thousands of users will frequenty design their Exchange servers.